The modified watch, in my experience, peculiarly appeals to the vanity of its creator rather more frequently than it does to those called upon to admire it. It is a construction of parts from disparate sources, commonly including cottage industry-produced components designed to fit the more popular models (usually divers watches) and aping the classic designs of the established marques. For obvious reasons, Seiko is a brand used most commonly by the ‘modder’ not least because of the easy availability of numerous donor watches from past and present and because they can be purchased relatively, or indeed, very, economically. Seiko appeals too because of the easy interchangeability of parts, particularly when you get your eye in and recognize compatibility between cases, movements, dials and hands. The most commonly modified Seiko watch is undoubtedly the SKX007 divers watch (see here for an example), rated to 200m and featuring the ubiquitous 7S26 movement. A few years ago, there was also a vibrant (after)market in parts for the 6309 divers (some examples here). Nowadays, Seiko 5 sports divers watches are being modified to resemble Blancpain 50 fathoms or Tudor Black Bays.

The subject of today’s adventure uses as its base the 6105-8110 diver of the early to late 1970’s, a watch occupying a pricing tier a notch or two higher than the common and garden 6309 and 7S26 divers and consequently not so commonly used as the basis of a modified watch. I would never normally dream of corrupting such a classic but have done so twice with a clear conscience. In the first case, it was as a pragmatic means to rid a basically decent example of a hateful aftermarket reproduction dial (see the first post in this here blog) but the basis of this present project was an empty but otherwise complete case purchased from Ebay and in need of a movement, dial and hands.

Any realistic ambition to return this to originality was greatly hampered by the very long odds on finding a decent original 6105 dial and so I saw this as an opportunity to have a stab at producing a day/date 6105. The obvious first question then is which movement to use. The closest day/date relative to the 6105 is the 6106 but that features a day/date quickset operated by pushing in the crown, and that is incompatible with the locking divers crown on the 6105 case. Fortunately, the later 6309 movement had the same dimensions as the 6105/6016 and even better, adopts a convention pull-out day/date quickset which works in the same way as the date quickset of the 6105B movement fitted to the second generation 6105 diver. However, an even nicer option, given that the 6105B is a hacking movement, would be to fit the 21 jewel 6306A, best known for its application in the Japan Domestic Market-only 6306-700x divers which were produced from about 1977. Rather than cannibalize a pukka 6306 diver, instead I sourced a JDM 6306 sports diver in ratty condition with a seized movement

So far then, we have a complete case, a movement desperately in need of a service but of course we also need a dial and hands. I’ll fess up at this point and confess that this particular project has been on the boil for a few years and has undergone a few false starts in order to find a dial/hand combination which I felt worked with the case. I’ve tried aftermarket Seamaster 300 style dials and Seiko sports diver dials but the only one I come back to which I think works coherently enough is the dial from a 6309-7040. The one I found is an original late Suwa dial, with a less pronounced bevel on the day/date aperture, but clearly a correct Seiko original. The lume was flaky though and so at this point I made two decisions, both of which faintly sacrilegious to the true Seiko faithful. The first was to remove the tab at 2 o’clock which in 6309 divers locks the dial to the indexed chapter ring in the case; the second was to have the dial relumed. Here’s the dial, minus its tab and half way through having its lume removed

The tab needed to come off for two reasons: first the chapter ring in the 6105 is not indexed and therefore does not need locking to the dial; and secondly the aperture in the case is not wide enough to admit a movement fitted with a 6309 dial still sporting its tab. The 6309 cases have an arc machined into the case at the appropriate location to allow sufficient clearance for the tab:

With the dial away with James Hyman for its relume, we can appraise the movement, dial side first.

With the day ring removed, it’s clearly been some time since this movement has had a service. I suspect much of the grot on this side has come from barrel grease migrating through from the lower barrel arbor hole in the mainplate. Turning it over, the main evidence of neglect lies in the accumulation of dirt/wear/grease on the ratchet wheel

and with that removed we see too on this side of the movement, barrel grease congealed around the upper barrel arbor hole in the barrel and train wheel bridge.

In fact, there was so much gloop that the barrel refused to part from the bridge

without rather more of a wrestle than should be the case

Having unglued the barrel, we have a chance to see one of the features which distinguishes the 6306 from the 6309 movement; the hacking lever

For the uninitiated, the hacking lever transfers longitudinal movement of the clutch wheel to the balance wheel such that when the crown is pulled out to the setting position, the lever will move against the balance wheel, stopping the watch. Its purpose is to allow the second hand to be synchronized with the minute hand so that the second hand passes through 12 at the same time as the minute hand passes through any given minute marker on the dial. With the rest of the disassembly completed smoothly, the parts are now ready for cleaning

The obvious problems deriving from the state of the barrel prompted further investigation. Popping the lid, and we see a very dirty looking mainspring, with in particular the barrel arbor completely clogged with congealed lubricant

With a clean, we get to see the mainspring uncoiled

ready to be refitted to the barrel

Now, let’s look at the second feature which distinguishes the 6306 from the 6309 movement. In every respect, bar the hacking lever and centre wheel bridge (which sports a groove in the 6306 to accommodate the hacking lever), the 6306 and 6309 movements are essentially identical from the train wheel bridge down. The bridge itself however, is where those additional four jewels lie.

Where the 6309 bridge has a single pivot jewel for the escape wheel, the 6306 bridge has Diafix settings supporting the escape and third wheels and a single pivot jewel serving the fourth wheel a net increase of four jewels. In contrast to the Diashock fitting which supports either end of the balance staff and whose dual role is shock protection and oil retention, the Diafix setting is there primarily to support oil retention and to protect the setting from contamination. The retaining spring therefore does not really serve the same purpose as the Diashock spring but is mostly there to keep the protecting jewel in place. With both Diafix springs and protecting jewels removed we see the naked settings and hole jewels

and a close up of one of the springs part way through being refitted over the cap jewel, post clean.

With everything clean, we can start to reassemble the movement

taking a look as we go at the kanji day wheel which is a feature of the Japanese domestic market models

Time to fit that relumed dial along with my current favourite default choice of Seiko hands to add a splash of colour

The lume colour, incidentally, had been very nicely matched to that of the hands by James Hyman who has also also followed the outline of the original lume with great precision. Before we fit the movement to the case, there is one last task to take care of. The original stem fitted to the crown was obviously a 6105 stem and is incompatible with the 6309/6 movement. I removed the original stem and fitted a 6309 dress watch stem but the problem with 6309 stems is that they are intended for cases with a wider bore crown tube and do not, therefore, fit down the relatively narrow 6105 tube.

Before fitting the dress stem then, I had to take off some material to narrow the stem at the offending position, enabling it to pass unhindered down the tube. Here’s a comparison of the modified 6309 stem fitted to the 6105 crown (top) with the crown and stem from the 6306 sports diver (bottom).

With that sorted, it’s time to fit the movement to the case

to which incidentally, I have fitted a high dome sapphire crystal

before fitting the turning ring

and finally an insert sourced from a modern Seiko quartz Tuna (the SBBN007)

Three more of the finished watch

and a slightly inept lume shot to complete the story

As I suggested at the start, there is always a danger with any modified watch that the end result is not necessarily something which will appeal to a more general audience anything like as much as it appeals to its creator. The internet is festooned with all manner of truly ghastly creations but also some beautifully judged and executed work. I don’t pretend any of mine fall into the latter category because in my increasingly infrequent diversions into moddery, I generally find myself running up blind aesthetic alleys only to really appreciate them as such when viewing them with fresh eyes after a period hidden away. But this one, at least in my opinion, just about hangs together sufficiently well to be sure that I won’t be returning to inflict any further tweaks.

Martin that is some very creative work on the 6105. I recently purchased a 6105-8000 (CASE ONLY) so I’m trying to build this from the ground up , I have plenty of 6309 dive movements lying around so I have that box checked but I need to source 6309 “dress” stem I have a question about that , should the donor stem be from a crown at 3:00 or 4:00 dresser or does it matter? Also can you highlight or circle where you “shaved” down the stem to fit ? Thank you and best regards,
Richard

The 6309 stem came from a watch material house as a spare part and not from a donor watch. The length, as far as I know, is standard and you trim to fit the case. You should be able to see from the comparison photo featuring the 6306 stem, the part of the stem that has been reduced. Good luck with your project.
Martin

Richard, no leads on a bezel I’m afraid. Just keep scanning Ebay and watch forum sales corners. If you have the turning ring but not the insert then you can adapt an insert from, say, an SKX007 but if the turning ring itself is missing then you may be in for a long wait.

Quick question for you. I’ve got the possible chance at buying a completely original 6105-8110 from my watchmaker. He has made comments about restoring them (more specifically early Seiko auto’s in general as he doesn’t seem to be aware of the movement differences) and noted that he was always having to up-jewel the movements because of the bushes wearing out.

I notice you do a similar method here by swapping the plate entirely.

My question is this – Which movement would be a good donor to use parts from to up-jewel a 6105 movement? Much in the same way you can use a 6306 to up-jewel a 6309.

Arguably the part most vulnerable to wear in the 6105 is the main plate barrel bush but there is no removable bush there and so any repair would probably require reaming and fitting of a separate bush. However, the architecture on the calendar side might make that problematic and even with space allowing, I suspect finding a matching jewel/barrel arbor pair might be challenging. Nevertheless, to answer your question, the only option for a higher jewel count main plate would be the high beat 6159 but the cost of that would most likely be prohibitive and a donor movement would be very difficult to source. None of the 6106 or 6119 variants will work because they use push quickset mechanisms that are incompatible with the design of the 6105 case tubes. So you are then stuck with the 6105A, 6105B or 6117, all of which are basic 17 jewel designs. However, the 21 jewel variants of the 6119 and 6106 could offer up higher jewel count bridges but you would then need to take care that the train wheels were compatible, say with a diafix setting at one end and a standard jewel or bearing at the other. The bottom line is that unless you want to swap out the 6105 with something like a 6306 or 6319, you are stuck with the 6105 main plate and 6119/6106 for other parts. Good luck!